Electrolytic separation of zinc from zinc oxid.



No. 642,933. Patented Feb. 6, I900. 0. J. STEINHART, J. L. F. VOGEL & H. E. FRY. ELECTROLYTIC SEPARATION OF ZINC FROM ZINC OXID.

(Application filed Apr. 10, 18 99.)

(No Model.)

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UNrrED STATES PATENT Orincs.

OSCAR JULIAN STEINHART, JULIUS LEONARD FOX VOGEL, AND HENRY ERNEST FRY, OF LONDON, ENGLAND; SAID STEINHART AND VOGEL ASSIGNORS TO SAID FRY.

ELECTROLYTIC SEPARATION OF ZINC FROM ZINC OXlD.

SPECIFICATION forming part of Letters Patent No. 642,933, dated February 6, 1900.

Application filed April 10, 1899. Serial No. 712,510. (No specimens.)

To aZZ whom it may concern.-

Be it known that We, OSCAR JULIAN STEIN- HART and JULIUS LEONARD FoX VOGEL, electrochemists, residing at 91 Blackfriars road, London, in the county of Surrey, and HENRY ERNEST FRY, mineral merchant, residing at 5 Laurence Pountney Hill, London, England, subjects of the Queen of Great Britain, have invented certain new and useful Improvements in the Electrolytic Separation of Zinc from Zinc OXid, of which the following is a specification.

The object of this invention is to reduce zinc oxid electrically into metallic zinc. This we client by dissolving zinc oXid in zinc chlorid kept fused by heat applied to the bottom of the vessel in which the reduction is to be eifected and by passing an electric current of low voltage through the molten bath, so that oxygen is evolved at the anode and zinc is deposited in a molten state and joins the oathode which is formed of a layer of molten zinc at the bottom of the vessel.

Zinc oXid, although being of itself an infusible compound, can be dissolved in a bath of molten zinc chlorid and forms with it a readily-fusible compound, which when acted upon by an electric current of suitable low voltage is decomposed in such manner that no chlorin is evolved so long as zinc oxid is present. Thus by continually feeding fresh supplies of oXid into the bath of molten zinc chlorid a continuous reduction of the oxid is obtained, the zinc chlorid present only actin g as a solvent. To the zinc chlorid it is advantageous to add a small quantity of sodium chlorid or other suitable salt capable of acting in like manner and which will render it less hygroscopic.

We efiect the reduction of zinc oxid in the above manner in any suitable vessel formed of or linedgwith refractory material. We prefer to use a shallow Vessel, such as shown in the drawings annexed.

In the drawings, Figure 1 is a cross-section of the vessel and the furnace-fines used for heating it on the under side. Fig. 2 is a longitudinal section, and Fig. 3 a plan, of the vessel.

In the figures, A is a vessel formed of refractory material.

B B are furnace-fines by which it is heated on the under side.

0 C are carbon blocks forming the cover and projecting downward into the vessel at a distance apart from one another to form the anode.

D is a layer of molten zinc at the bottom of the vessel, serving to form the cathode.

E E are openings in the cover by which zinc 6o oxid may from time to time be fed into the vessel. E are lids by which these openings can normally be kept closed.

F is an outlet for any gas produced in the interior of the vessel. The bottom of the vessel is kept heated just sufficiently to keep the layer of zinc at the bottom of the vessel in a melted state.

A channel G, leading upward from the bottom of the vessel for a short distance to an overflow-spout G, allows molten zinc to flow off, and so the layer of molten zinc at the bottom of the vessel is always kept approximately at one uniform level.

I is a conductor for carrying current to-molten zinc at bottom of vessel.

\Vhen commencing to work, sufficient zinc is first placed in the vessel to form when melted a layer about one inch deep, and then zinc chlorid previously dehydrated is introduced in sufficient quantity to form when melted a layer,'say, about two inches deep, which floats on the top of the zinc.

The dehydratedzinc chlorid employed is preferably obtained by evaporating zincchlorid in a partial vacuum in the manner described in our application for patent, Serial No. 712,511, filed April 10, 1899; but other methods, even for partially dehydrating the zinc chlorid, could be used, andin such a case all the remaining water would be at once removed when it had been melted and the current passed through. I

The carbon plates which form the anode are made of such a length that their lower ends are immersed about one inch in the zinc chlorid and are consequently distant about one inch from the surface of the molten zinc.

A quantity of zinc oxid previously purified is now introduced into the cell and drops down onto the surface of the molten zinc, some of it becoming dissolved in the chlorid. Afterward electric current of low voltage say about three volts-is passed through the molten chlorid, the molten zinc at the bottom of the vessel forming the cathode and the carbon plates the anode, the oxid dissolved in the molten chlorid is decomposed, oxygen being evolved at the anode and zinc inamolten state deposited at the cathode. As the zinc oxid fed into the Vessel becomes gradually dissolved in the molten chlorid fresh zinc oxid is from time to timeadded,andin this way a continuous reduction is obtained.

By keeping the vessel heated externally just sufficiently to keep the zinc at the bottom of the vessel in a melted state we are able to use an electric current of lower voltage than would otherwise be practicable if the required heat were to be applied by the current passing, and can so insure that the oxid only shall be decomposed and not the chlorid, while at the same time the carbons are not materially heated by the passage of the current and are not so quickly consumed as they otherwise would be.

That we claim is- 1. The process herein described of separating zinc from zinc oxid, which consistsin dissolving zinc oxid in molten zinc chlorid, heated to a temperature just above the meltingpoint of zinc, passing an electric current of low voltage through the molten mixture be tween a layer of molten zinc at the bottom, forming the cathode, and a conductor which dips into the molten mixture of chlorid and oxid, and forms the anode, and from time to time adding fresh zinc oxid to the vessel as oxid is decomposed by the current, to maintain at all times undissolved oxid resting on the molten zinc in close proximity to the lower end of the conductor forming the anode.

2. The process herein described of separating zinc from zinc oxid, which consists in dissolving zinc oxid in molten zinc chlorid mixed with sodium chlorid, heating the zinc chlorid to a temperature just above the melting-point of zinc, passing an electric current of low voltage through the molten mixture between a layer of molten zinc at the bottom, forming the cathode, and a conductor which dips into the molten mixture of zinc chlorid and oxid, and forms the anode, and adding from time to time fresh zinc oxid to the vessel as oxid is decomposed by the current.

3. The process herein described of separating zinc from zinc oxid, which consists in dissolving zinc oxid in molten zincchlorid,heated to a temperature just above the meltingpoint of zinc, passing an electric current of low voltage through the molten mixture, and from time to time adding fresh oxid to the bath to maintain continuously a supply of undissolved oxid resting on the molten zinc forming the cathode and the end of the elec tric conductor forming the anode.

OSCAR JULIAN S'llfilNlIAlt'l. JULIUS LEONARD FOX VOGEL. lllll ltl' ERNEST FRY.

\Vitnesses as to the signatures of Oscar Julian Steinhart and Julius Leonard Fox Vogel:

FRED. G. HARRIS, GEO. J. B. FRANKLIN.

Witnesses as to the signature of Henry Ernest Fry:

HENRY BLANCHARD STUNT, G. F. VARRENL 

